Here’s a handy tip from the codex. If you want to use a shortcode outside of the WordPress post or page editor, you can use this snippet to output from the shortcode’s handler(s):
// Use shortcode in a PHP file (outside the post editor). <?php echo do_shortcode('[gallery]'); ?>
Replace with the shortcode you want to use. More information is available in the WordPress codex on the do_shortcode function page.
